Polyethylene vibrations

Tchenio P, Myers A B and Moerner W E 1993 Vibrational analysis of the dispersed fluorescence from single molecules of terrylene in polyethylene Chem. Phys. Lett. 213 325-32... 

Figure 6 Vibrational spectra of polymers, (a) Transmission infrared spectrum of polyethylene (b) electron-induced loss spectrum of polyethylene (c) transmission infrared spectrum of polypropylene. ...

Both vibrational spectroscopies are valuable tools in the characterization of crystalline polymers. The degree of crystallinity is calculated from the ratio of isolated vibrational modes, specific to the crystalline regions, and a mode whose intensity is not influenced by degree of crystallinity and serves as internal standard. A significant number of studies have used both types of spectroscopy for quantitative crystallinity determination in the polyethylenes [38,74-82] and other semi-crystalline polymers such as polyfethylene terephthalate) [83-85], isotactic poly(propylene) [86,87], polyfaryl ether ether ketone) [88], polyftetra-fluoroethylene) [89,90] and bisphenol A polycarbonate [91]. 

Here m is the mode order (m — 1,3,5. .., usually 1 for polyethylenes), c the velocity of light, p the density of the vibrating sequence (density of pure crystal) and E the Young s modulus in the chain direction. The LAM band has been observed in many polymers and has been widely used in structural studies of polyethylenes [94—99,266], as well as other semi-crystalline polymers, such as poly (ethylene oxide) [267], poly(methylene oxide) [268,269] and isotactic poly(propylene) [270,271], The distribution of crystalline thickness can be obtained from the width of the LAM mode, corrected by temperature and frequency factors [272,273] as ... 

Figure 9.29 XPS, FTIR and RBS of a CrO,ySi02/Si( 100) after polymerization of ethylene at 160 °C all reveal the presence of a significant amount of polyethylene, visible in the C Is peak in XPS, the symmetric and asymmetric C-H stretch vibrations of CH2 groups in transmission IR, and a C peak in RBS (adapted fromThiine etal. [92]).

Snyder, R.G, Vibrational study of the chain conformation of the liquid n-paraffins and molten polyethylene, J. Chem. Phys., 47, 1316, 1967. 

Organic polymers and resins have also been used for zeolite binding. An early example is the use polyurethane in the formahon of vibration-resistant zeolite porous bodies for refrigerant drying [90]. Organic binders such as cellulose acetate and other cellulose-based polymers have also used to mitigate problems with binder dissolution in aqueous phase separations [91, 92]. Latex has also been used as a water-stable organic binder [93]. More recently, thermoplastic resins, such as polyethylene have also been used as binders for zeolites [94]. 

S.E. Barnes, E.C. Brown, M.G. Sibley, H.G.M. Edwards, I.J. Scowen and P.D. Coates, Vibrational spectroscopic and ultrasound analysis for in-process characterization of high-density polyethylene/polypropylene blends during melt extrusion, Appl. Spectrosc., 59, 611-619 (2005). 

Atomic polarization is attributed to the relative motion of atoms in the molecule effected by perturbation by the applied field of the vibrations of atoms and ions having a characteristic resonance frequency in the infrared region. The atomic polarization is large in inorganic materials which contain low-energy-conductive bonds and approaches zero for nonpolar organic polymers, such as polyethylene. 

The state of polarization, and hence the electrical properties, responds to changes in temperature in several ways. Within the Bom-Oppenheimer approximation, the motion of electrons and atoms can be decoupled, and the atomic motions in the crystalline solid treated as thermally activated vibrations. These atomic vibrations give rise to the thermal expansion of the lattice itself, which can be measured independendy. The electronic motions are assumed to be rapidly equilibrated in the state defined by the temperature and electric field. At lower temperatures, the quantization of vibrational states can be significant, as manifested in such properties as thermal expansion and heat capacity. In polymer crystals quantum mechanical effects can be important even at room temperature. For example, the magnitude of the negative axial thermal expansion coefficient in polyethylene is a direct result of the quantum mechanical nature of the heat capacity at room temperature." At still higher temperatures, near a phase transition, e.g., the assumption of stricdy vibrational dynamics of atoms is no... 

Polymers, with their highly stereoregular structures, are frequently of sufficiently high symmetry for infrared spectroscopy to give only an incomplete picture of the vibrational characteristics of the compounds. In some, as many as half of the fundamental modes are infrared inactive. These non-absorbing modes can frequently be observed in the Raman effect (e.g. polyethylene where mutual exclusion" applies and at least eight modes are Raman active and infrared silent ). 

Rotation of the core (or its reciprocating rotary vibration) can be even more efficient in processing of high-viscous melts, for example, filled polymers, high- and superhigh-molecular polyethylene (with MM > 10s). We may assume that this is dependent upon two major causes. The introduction of a filler results in a changed spectrum of relaxation time H(9) 41-42-45). Thus, for example, introduction of 10% of chalk (by volume) into polyolefins shifts the spectrum along the axis of coordinates towards... 

Fig. 12. Tentative flow curves of low-density polyethylene with MFI = 2.0 g/10 min extruded at 170 °C through channels with a two-angle ellipse Wber cross section with a length of 50 (a), 75 (b), and 100 (c) mm with reciprocating-rotary vibration of the element in the zone upstream of the inlet to the channel (according to the diagram given in Fig. 9) ...

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